| JP Air-Conditioning Services Limited | Energy | 2012 |
| JP Catering London Ltd | Hospitality | 2025 |
| JP Drainage Solutions Ltd | Water & waste | 2024 |
| JP Music Tuition Limited | Education | 2022 |
| JP Renovations (South East) Limited | Real estate | 2015 |
| JPM Lettings Limited | Real estate | 2025 |
| JPS Properties Holdings Limited | Real estate | 2021 |
| JR Premises Limited | Real estate | 2023 |
| JR Roofing Group Ltd | Construction | 2025 |
| JRB Surfacing Ltd | Construction | 2020 |
| JS Burgers Ltd | Hospitality | 2025 |
| JS ENC Ltd | Hospitality | 2018 |
| JS Prime Properties Ltd | Real estate | 2025 |
| JS Resilience and Leadership Advisory Limited | Professional & scientific | 2023 |
| JSB Limited | Other services | 2019 |
| JSC Fernandez Ltd | Administrative & support | 2015 |
| Jsheeba Services Limited | Health & social care | 2016 |
| JSL Talent Partners Limited | Administrative & support | 2026 |
| JSP Heating Ltd | Construction | 2019 |
| JSR Customise Ltd | Construction | 2023 |
| JT Commerce Ltd | Wholesale & retail | 2025 |
| Jtac Event Services Ltd | Information & communication | 2024 |
| JTB Logistics Limited | Wholesale & retail | 2019 |
| Jtopia Productions Limited | Information & communication | 2012 |
| Jtorred Limited | Health & social care | 2025 |
| JTX Logistics Ltd | Transport & logistics | 2025 |
| JU Prestige Homes Limited | Real estate | 2025 |
| Jubbers Productions Ltd | Arts & recreation | 2023 |
| Jubet Court Management Limited | Real estate | 1973 |
| Judd Design Innovation Ltd | Professional & scientific | 2018 |
| Judge & Priestley (UK) Limited | Professional & scientific | 1991 |
| Judge & Priestley Limited Liability Partnership | | 2005 |
| Judicaël Group Ltd | Manufacturing | 2026 |
| Juefang Yang Limited | Wholesale & retail | 2019 |
| Juicy Purr Limited | Other services | 2023 |
| Juju Tech Ltd | Information & communication | 2022 |
| Juleacleans Ltd | Administrative & support | 2026 |
| Julia Conroy Limited | Professional & scientific | 2018 |
| Julian Roofing Services Ltd | Construction | 2022 |
| Julie Rose Recruitment Limited | Administrative & support | 2010 |
| Julie Van Leer Pilates Limited | Other services | 2014 |
| Juliette Schmidt Events Limited | Administrative & support | 2017 |
| Juna Retail Ltd | Other services | 2020 |
| Jungle Monkeyz Enterprise Limited | Arts & recreation | 2025 |
| Jungle Monkeyz Holding Ltd | Financial services | 2023 |
| Jungle Monkeyz LLP | | 2013 |
| Jungle Monkeyz Productions Ltd | Information & communication | 2026 |
| Jungle Monkeyz W12 Limited | Arts & recreation | 2024 |
| Jupiter Confectionery Group Limited | Wholesale & retail | 1987 |
| Jusb Limited | Education | 2003 |
| Just Cleaning & Removals Limited | Transport & logistics | 2019 |
| Just Delivery Service Limited | Transport & logistics | 2022 |
| Just Finishing Solutions Limited | Manufacturing | 2008 |
| Just Kidz Oosc Ltd | Education | 2016 |
| Just LIL Music Ltd | Information & communication | 2025 |
| Just Williams Holdings Limited | Financial services | 2025 |
| Just Williams Toys Ltd | Wholesale & retail | 2008 |
| JUST4YOUSHOPPING Ltd | Wholesale & retail | 2024 |
| Justin Plaza (Mitcham) RTM Company Limited | Real estate | 2017 |
| Juvenile Asia Limited | Information & communication | 2026 |
| Juvpeti Trans Limited | Transport & logistics | 2017 |
| JWC Construction Ltd | Construction | 2020 |
| JWC Holdco Limited | Financial services | 2023 |
| JWC Property Development Limited | Construction | 2023 |
| JWP1 Ltd | Real estate | 2024 |
| JWP2 Ltd | Construction | 2025 |
| Jyothy Limited | Administrative & support | 2019 |
| K & a Beauty Ltd | Other services | 2017 |
| K & K Express Limited | Transport & logistics | 2013 |
| K Bradley Engineering Ltd | Professional & scientific | 2014 |
| K C S (Bromley) Equipment Ltd | Wholesale & retail | 2009 |
| K Creative Limited | Information & communication | 2020 |
| K D Technical Ltd | Construction | 2015 |
| K Fit Studio Limited | Arts & recreation | 2026 |
| K Industries Ltd | Extraterritorial | 2013 |
| K LIS Building Services Ltd | Construction | 2022 |
| K Sodipo Consultancy Ltd | Professional & scientific | 2017 |
| K&F Heavy Equipment Sales Ltd | Wholesale & retail | 2025 |
| K&L Research Limited | Professional & scientific | 2014 |
| K&P Global Ltd | Wholesale & retail | 2019 |
| K-Team Architecture Ltd | Professional & scientific | 2014 |
| K-Tech Heating Limited | Construction | 2015 |
| K. Tinies Limited | Health & social care | 2025 |
| K.I.T. Education Ltd | Education | 2026 |
| K.N. Carpentry & Building Services Limited | Construction | 2023 |
| K1 Electrical Services Ltd | Construction | 2014 |
| K2 GAS Plumbing & Heating Limited | Energy | 2025 |
| K2 Limited | Professional & scientific | 2015 |
| Kaanthal Ltd | Wholesale & retail | 2022 |
| Kaemelog Limited | Wholesale & retail | 2022 |
| Kailash Accountancy Ltd | Professional & scientific | 2025 |
| Kakamaq Limited | Wholesale & retail | 2020 |
| Kalbert Healthcare Limited | Administrative & support | 2025 |
| Kali RXS Ltd | Health & social care | 2026 |
| Kamala Care Service Ltd | Health & social care | 2021 |
| Kamali Kultur Limited | Extraterritorial | 2023 |
| Kamau Group Ltd | Wholesale & retail | 2025 |
| Kamfaz Investment Limited | Administrative & support | 2020 |
| Kamsiv Consultancy Limited | Professional & scientific | 2023 |
| Kane Court (SE10 0JR) RTM Company Limited | Households | 2025 |